body {
  margin: 4px;
  font-family: Helvetica;
  
  /* Centering & Limit Width */
  margin: auto;
  width: 720px;
}

.masonry {
  column-count: 4;
  column-gap: 0;
}

.item {
  padding: 2px;
  position: relative;
  counter-increment: item-counter;
}

.item img {
  display: block;
  width: 100%;
  height: auto;
}

.item::after {
  position: absolute;
  display: block;
  top: 2px;
  left: 2px;
  width: 24px;
  height: 24px;
  text-align: center;
  line-height: 24px;
  background-color: #000;
  color: #fff;
  content: counter(item-counter);
}